A continuation of studies on different aspects of alphafetoprotein (AFP), the fetal protein associated with hepatomas and teratomas, is proposed. 1. We have recently developed a new purification procedure for bovine AFP. This method has allowed the purification of gram quantities of AFP. We now propose to carry forth the work on the amino acid sequence of AFP making use of this supply of bovine AFP. Our earlier studies have established amino acid sequence homology of AFP with albumin. 2. We have recently found that AFP binds bilirubin. This, and the structural similarity with albumin, suggests that other small molecules may show such binding. We propose to test AFP for binding of various small molecules weight ligands, especially ones that could influence cell differentiation and functions of immune cells. 3. We have recently noticed that human AFP has a subfraction which does not bind to concanavalin A. The amount of this subfraction is much higher in the AFP of teratocarcinoma patients. Some hepatoma sera also seem to have an elevated proportion of the nonbinding variant. These findings have opened new possibilities in the use of AFP in tumor diagnosis. It could allow a diagnostically useful distinction between cirrhosis and hepatoma if the AFPs produced in these conditions are different. We also propose to attempt to develop antisera specific for the subtypes using hybridomas. 4. We will prepare homogenous hybridoma antibodies to human AFP. Such antibodies, when well characterized and widely distributed, could remove one variable from the AFP assay. Some of them may be specific for the subtypes mentioned above. We also propose to utilize the hybridoma technology to produce large amounts of mouse antibodies to mouse AFP for use in immunotherapy experiments.